My mushrooming mentor taught me that mushrooms reproduce from spores which are dropped by the cap, but your question has given me pause… I really, really hope we haven’t been depleting the mushroom population by harvesting them improperly. I’ve done a bit of online research and I’m concluding that the stern warnings of your mushroomer friends are good ones to abide by. It sounds like mushrooms reproduce both from above (spores dropped from the caps) and below (mycelium and ectomycorrhizae), so that it is best to cut the stem, leaving some of the base in the ground.

For the super duper long answer to your question, here are some great links and a bit of what I’ve found online:

This from the Forest Service website (http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/fsm9_034421.pdf):

“Don't leave holes in the duff. It dries out the fertile ground underneath. Mushrooms are thefruit of a mycelium, an invisible web of threads that lives in the ground year round. Holesin the duff can dehydrate and shrivel the mycelium so that it eliminates mushroom fruiting. If you pick up duff to check out a promising mound or you leave a hole when you pick a mushroom, put the duff back when you're done. And be sure not to rake the duff to look for mushrooms -- it's very damaging to the mycelium. Do carry your picked mushrooms in a basket, mesh bag, or bucket with holes drilled in it. A picked mushroom continues to drop spores. By carrying it in an open-air container, you help it distribute spores so the mushroom can reproduce. Carrying mushrooms in a closed container eliminates spore dispersal.”

Also from the Forest Service, in reference to King Boletes (http://www.fs.fed.us/pnw/pubs/gtr513/gtr513f.pdf):

“Harvest techniques: Plucked or cut”

“Plucked” seems like what I’ve been doing, and the Forest Service is saying that is an acceptable method, but since both of the regeneration methods listed in the same document (“Regeneration after harvest: Perennial mycelium and ectomycorrhizae”) are things that occur underground, it again seems like it’s best to leave the base undisturbed.

In an online guide to growing King Stropharia mushrooms, (http://www.backyardbountycollective.com/files/stropharia.doc) it says to “harvest mushrooms gently with a twisting action to avoid disturbing the mycelium and undeveloped ‘pins’.”

And from this site:(http://www.twineagles.org/edible-wild-mushrooms.html):

“Ethical harvesting means giving the mushrooms the opportunity for spore production in the future. For some mushrooms it can take up to 10 days for spores to drop after they have popped up. Many foragers use the term "rule of thumb" which means if it's smaller than your thumb, don't pick it. Given that there are so many variables involved in mushroom growth and reproduction, I suggest going to the lowest common denominator and never uproot the full mushroom when you gather. As well, do not over-harvest and mindfully leave a portion of mushrooms unpicked.Harvesting edible wild mushrooms is like picking any other kind of delicate fruit or berry; they need to be carefully gathered so that we minimize our disturbance in their environment. This is one of the best ways we can show our gratitude and respect for the mushrooms and all the other life present there. When you're gathering, I suggest you cut the mushroom instead of pulling it from the ground and cover the area with a 1/2 inch of leaf litter where you've gathered once you're done. This gives the cut stalks a duff or debris layer once their fruit bodies are gone.”

Thank you so much for the question; we’ll be better, more ethical mushroomers now!